The present invention generally relates to turbine nozzles and, more particularly, to variably adjustable flow turbine nozzles.
In an air cycle machine or other turbomachinery, a turbine may include a turbine nozzle at the turbine inlet that may channel the combustion gases between the turbine rotor blades that extract energy therefrom for powering the compressor.
Turbine nozzle flow is an important performance characteristic in most turbomachinery and specifically in an air cycle machine. It is difficult to manufacture drilled or machined nozzles that have small nozzle-to-nozzle variation. This difficulty results in significant rework and/or expensive manufacturing processes. Conventional turbine nozzles may be manufactured by first drilling or machining the nozzle flow passages, measuring the nozzle flow and adjusting the nozzle flow by extrude honing. A typical extrude honing process may, for example, pump clay and abrasive through the nozzle passageways to make the passages larger in size, thereby increasing nozzle flow. The airflow measurement step and the airflow adjustment step are repeated until the desired nozzle flow is achieved. Typically, nozzle flow must be controlled to within about +/−1%.
A variable geometry turbine has been disclosed in U.S. Pat. No. 6,652,224. The turbine described in the '224 patent has nozzle vanes that are displaceable across the turbine inlet flow path into slots. The vanes have cut-outs which reduce the vane cord and permit peak turbine efficiency over a range of geometries. Nozzle flow may be adjusted by controlling the axial position of a nozzle ring. Unfortunately, additional components, such as axially extending pins and stirrup members may be necessary to control the nozzle ring's axial position (col. 4, lines 1–17).
As can be seen, there is a need for an improved turbine nozzle and method for adjusting the flow through the turbine nozzle.